


Born Beta

by omegadeanlovesalphacas



Category: Supernatural
Genre: Alpha Castiel, Alpha Castiel/Omega Dean Winchester, Alpha/Beta/Omega Dynamics, Bottom Dean, Claiming, Dominance, Fighting for Dominance, First Time, Fluff and Smut, Knotting, M/M, Mildly Dubious Consent, Omega Dean, Smut, Submission, Top Castiel
Language: English
Status: Completed
Published: 2016-11-02
Updated: 2016-11-02
Packaged: 2018-08-28 14:04:27
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 874
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8449015
Author URL: https://archiveofourown.org/users/omegadeanlovesalphacas/pseuds/omegadeanlovesalphacas
Summary: Everyone is born a beta, only to become either an Alpha or an omega when they first mate. Both Dean and Castiel are determined to be the Alpha.





	

**Author's Note:**

> Warning! This is an Alpha/omega kink prompt fill. Expect more porn than plot, and lots of power imbalance between Cas and Dean. Mind the warnings and kinks in the tags.
> 
> the-grey-panther asked:  
> AU: Everyone is a Beta by default, until they're bonded. If you receive a mating mark, you automatically turn into an Omega. If you do the claiming, you become an Alpha. Dean and Castiel are in love, but they both want to be the Alpha. Cue naked wrestling, during which Cas manages to land a bite on Dean. Then they mate, with Dean being kinda huffy because he lost.
> 
> Filled on Tumblr, April 2015.

Tonight was the night, they had decided. They were already naked and in bed, but this was just the warm up. Soon they would be _mated_.

“I’m going to be the Alpha,” Castiel said confidently, pushing Dean over on his back and kissing him. 

Dean laughed between kisses, rolling them over so he could be on top. “Not on your life, you’re going to be the omega,” Dean said, just as confidently, kissing Castiel back.

Castiel thrust his hips up against Dean’s, groaning as his hard cock pushed  against the other beta’s skin. “Ready?”

Dean’s breath quickened and he nodded. “Yeah.”

Castiel responded by shoving roughly at Dean, flipping him onto his back. Dean yelped in surprise, but managed to squirm out from under Cas before he could get a hold. “Cheater!” he cried out with a laugh as he pulled himself up into a crouch on the bed, squaring off against Castiel. 

Cas grinned, lunging at Dean. “Alls fair in love and mating,” he gasped out, knocking Dean back onto the bed. He tried to get a hold on Dean, but slipped and they both rolled off the bed and hit the carpeted floor with a thump. 

Cas groaned but scrambled up to his knees quickly before Dean could grab him. Dean lunged at him, but Castiel managed to dodge, and Dean landed on his chest on the floor. Castiel saw his opening and he jumped on Dean’s back, holding him to the floor with his weight and grabbing both his arms in his hands, pinning them to Dean’s back. 

Dean grunted in frustration, trying to buck Castiel off, but he was pinned. Castiel shifted, pushing his hips back until his hard cock was nestled between Dean’s round ass cheeks. He bent and pressed an open mouthed kiss to the back of Dean’s neck. Dean started to buck again when he realized what was coming, and Castiel bit into the sensitive skin before he could stop him. 

Dean let out a little whimper as he felt his body submit to his new Alpha. “Damn it,” he muttered. He could already feel wet slick in his channel, and he groaned when he realized his body was preparing to be taken.

Castiel grinned, kissing the fresh mating mark. “My good little omega,” he teased, letting go of Dean’s hands and reaching down for Dean’s hole. “Already wet for me,” he observed, pressing a finger inside.

Dean gasped as he was breached for the first time, surprised and a little annoyed at how good it felt. He let out an involuntary moan when Castiel replaced the one finger with two, and he pouted even as he pushed his ass back against Castiel’s hand.

“Gonna knot you now,” Castiel said, pulling out his fingers and wiping the slick on Dean’s ass. He lined his hard cock up to Dean’s wet hole, and started to slowly push in.

Dean gasped as the thick cock sunk into him, filling him up. He whimpered when Castiel was fully seated inside him, and he moaned out an involuntary “Alpha!”

Castiel took that as his cue, and he pulled out, only to thrust back in firmly. He enjoyed the surprised grunt that came from Dean, and he started to thrust steadily. “My omega,” he groaned, enjoying the way it felt to say the words. “Mine.”

“Yours, Alpha,” Dean replied on instinct, mind going fuzzy with pleasure and submission. He moaned when he felt Castiel’s knot start to grow for the first time, stretching him open and pressing into his prostate on each thrust.

Castiel already knew this wasn’t going to last long, and he grunted as he thrust harder, hips slapping against Dean’s ass as he fucked him. “Mine,” he repeated.

Dean could no longer speak, all he could do was whimper and moan as his Alpha took him, used him, fucked him. It was amazing and perfect and mind blowing, and the next thing Dean knew he was coming hard, the knot pushing him over the edge. 

Castiel was just as close, and he grunted as he slammed into Dean and came, knot locking them together and pumping seed into his omega. He collapsed onto Dean’s back, pinning him to the floor under his weight. He just lay there for a long moment, catching his breath and enjoying the pleasure of his knot. 

Dean’s head was spinning as he came down from his orgasm, and he was shocked to discover he loved the feeling of being split open on a knot. He let out a deep sigh, feeling a little disappointed to be an omega, although he could feel his new instincts starting to override that disappointment. 

Castiel pulled them over on their sides, giving Dean no choice but to let himself be manhandled. Cas wrapped an arm around Dean and pressed a kiss to the back of his neck. “I love you. You know I’m going to take good care of you, right?”

Dean nodded, craning his neck to look back at Castiel. “Yeah, I know you will, Cas. And I love you, too.” He smiled a little. “You know, being knotted was a lot more fun than I thought it would be.”

Cas grinned. “Just wait for round two.”

**Author's Note:**

> Thanks for reading! Comments are love! <3
> 
> Visit me on Tumblr: [omegadeanlovesalphacas.tumblr.com/mobilemenu.](http://omegadeanlovesalphacas.tumblr.com/mobilemenu)


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